Structures and properties of the copper(II) and nickel(II) complexes of NN′-bis[(2-hydroxy-5-methylphenyl)phenylmethylene]-4-azaheptane-1,7-diamine and related compounds: direct comparison of d8 and d9 analogues

Abstract

The nickel(II), copper(II), and zinc(II) complexes of the quinquedentate ligands mbp and cbp, derived from the Schiff-base condensation of 3,3′-iminobis(propylamine) with 2-hydroxy-5-methylbenzophenone (mbp) and 5-chloro-2-hydroxybenzophenone (cbp), have been investigated by magnetic, spectroscopic, and X-ray crystallographic techniques and shown to be five-co-ordinate monomers, the Cu compounds having normal magnetic moments while the Ni complexes are high spin. The e.s.r. spectra of the Cu complexes show ligand hyperfine splitting for two of the three nitrogen donor atoms, in agreement with X-ray structural observations for [Cu(mbp)]. The metal environments are approximately distorted trigonal bipyramids, but the Cu complex has one elongated Cu-N bond, which suggests distorted square pyramidal geometry, and a weaker ligand-field than for the Ni complex. Failure to observe ligand hyperfine contribution by this nitrogen to the e.s.r. spectrum of [Cu(cbp)], in either frozen chloroform or solid solution in the (isomorphous) Zn^II analogue, can be rationalised by the assumption that the Cu complex has essentially the same structure in the Zn lattice as in the pure Cu complex and in chloroform solution.

Crystal structures for [Cu(mbp)] and [Ni(mbp)] were determined by the heavy-atom method from counter data, and refined by full-matrix least-squares: [Cu(mbp)], space group P, Z= 2, a= 10.073(2),b= 12.438(3), c= 13.080(3)Å, α- 73.89(2), β= 67.54(1), γ= 86.99(2)°, R 6.3%. 2569 reflections; [Ni(mbp)], space group Pcnb, Z= 4. a= 16.927 (2), b= 24.232(2), c= 7.1562(7)Å, α=β=γ= 90°, R 6.1%, 1271 reflections. The Zn^II complex [Zn(cbp)] is isomorphous with [Cu(mbp)].